Delivery of North West Water's vital new sewage sludge incinerator in just 100 weeks resolved a looming environmental compliance crisis and added an elegantly discreet industrial facility to the landscape around Widnes.
Resolving how to dispose of sewage sludge from the five million population of the Manchester and Liverpool conurbations in a way that would meet new EC Directives developed into a daunting problem for North West Water.
Dumping the bulk of this material at sea either as processed sludge from inland sewage works or directly as raw sewage through dozens of outfalls into the Mersey estuary, had been the normal practice for a century or so.
Two decades of construction work on interceptors and treatment works had dealt with the raw sewage problem. By the early 1990s NWW was disposing of 2M.m3 of sludge a year from six waste water treatment works by pumping it via 86km of mains to a ship loading terminal at Liverpool. Then came a Directive giving notice that disposal at sea had to stop by 31 December 1998.
Analysis of the problem demonstrated that incineration was the most appropriate option. And the existence of the pumping main across the Mersey Valley allowed considerable flexibility in the choice of where to build the plant. A list of some 58 possible sites was narrowed to six and then to one.
But no matter how well engineered, sludge incinerators are perceived as bad for a neighbourhood. NWW found that despite extensive work on an environmental impact study of the Shell Green site at Widnes and many public meetings, it nonetheless had to go to a public inquiry.
The Directive deadline was looming but it was 18 months before approval was given. Construction had to start almost immediately after the decision was delivered, and so design had been moving forward to allow rapid progress on site.
But appearance was not forgotten. A rectangular shed 30m high and some 200m by 80m in plan would have served as an envelope to the pipes, presses, fluidised bed furnaces and exhaust scrubbers that are the basic elements of the plant. Instead, a cluster of structures whose dominant feature is the elegant curved outline of the main enclosure, has turned the complex into a visual asset of the industrial landscape.
Safety and cost were also paramount concerns. The 'zero tolerance for safety discrepancies' site charter defined a culture in which there were no lost time accidents in two million hours of work. The original budget figure was beaten by 20%. And the project was delivered and up and running just in time.
'This is an outstanding example of how a good team can deliver a major project to a very tight deadline. Early architectural input, value engineering and design for buildability and operational efficiency have produced a high quality complex constructed with a superb safety record.'
North West Water
Bechtel Water Technology
Tarmac Construction International
OSC Process Engineering (incineration process contractor)
USF (Edwards & Jones) (dewatering plant subcontractor)